Alloy wrought iron and article made therefrom



Patented June 16, 1942 ALLOY WROUGHT IRON AND ARTICLE THEREFROM John W.Davis, Tarentum, Pa., and Ray McBrian,

Denver, 0010. v

No Drawing. Application September 19, 1940, Serial No. 357,440

4 Claims. (C1. 75-123) Our invention relates to alloy Wrought iron andarticles made therefrom such as stay-bolts which have to maintain a highdegree of strength up to temperatures in the neighborhood of around 900F. and which, when in'use, are subjected to vibratory stresses, enginebolts which, when in use, are subjected to vibratory stresses and insome instances to approximately the same temperatures, and otherarticles which have to maintain a high degree of strength undervibratory stresses and relatively high temperatures.

Stay-bolts, engine bolts and many other articles are still manufacturedfrom wrought iron of the types known as refined bar iron and doublerefined iron, even though the cost of such wrought irons is in excess ofmany of the modern alloy steels.

Wrought iron of the grades now used in the manufacture of these articleshas a tensile strength, lbs. per sq. in. (p. s. i.) of from about 47,000to 52,000 at room temperatures and around 70,000 at about 400 F. Above400 F., the tensile strength drops fairly rapidly, for example, at about750 F., it is from about 32,000 to about 33,000 lbs. per sq. in. and atabout 900 F. from about 18,000 to about 20,000.

Stay-bolts not only require high tensile strength at room temperatures,but since they are used in modern locomotives they require high tensilestrength at elevated temperatures 'as well. Staybolts, as well as enginebolts, not only require high tensile strength, but must be capable ofwithstanding vibratorystresses over long periods and must also bereadily machineable.

An object of this invention is to produce an alloy wrought iron for usein the manufacture of stay-bolts, engine bolts and other articles havinga materially increased tensile strength at room temperatures and attemperatures ranging up to about 900 F. over the same articles made fromtypical double refined wrought iron.

Another objectis to produce articles such as stay-bolts and engine boltsfrom an alloy wrought iron containing from about .10% to about 1.00% ofmolybdenum and having a yield point p. s. i. at about 900 F. of fromabout 5,000 to about 8,000 greater than similar articles made fromtypical double refined wrought iron.

An object of this invention is to, produce Wrought iron containingmolybdenum in appreciable amounts up to about 1.00 and which ischaracterized by a. tensile strength when at 750 F., of from 5000 to6000 lbs. per sq. in. greater than typical wrought iron.

A further object is to produce wrought iron having a yield point p. s.i. at 750 F. of from about 4000 to about 6000 greater than typicaldouble refinedf wrought iron.

A still further object is to produce an alloy wrought iron having ayield point p. s. i. at 900 In comparative vibratory tests made on barsof double refined Wrought iron having a molybdenum content of from about39% to about 43% and bars of the same type of wrought iron but withoutmolybdenum, the bars containing molybdenum withstood an average of272,000 vibrations as against an average of 109,800 vibrations for thebarscontaining no molybdenum.

We prefer to manufacture our alloy wrought iron by the hand puddlingprocess, and in such process, we prefer to use what is known as theroasting method as distinguished from the scaling method, although wehave obtained quite satisfactory results with the scaling method.

' In the roasting method, after charging the pig iron, the furnace isclosed, and by handfiring for a period of from 40-50 minutes the pigiron .becomes a moltenmass which is then permitted .to roast for a,period of from 20-25 minutes.

Roasting is simply a firing operation with the damper of the furnace upor flying, during which period some carbon, phosphorus and sul-' phurare removed. We have found that satisfactory results are obtained byadding to the molten iron immediately before beginning the roastingperiod, a sufiicient quantity of molybdenum to obtain the molybdenumcontent defollowing composition:

Per cent Molybdenum tri-oxide -75 Carbon; max 12.0 Iron, max 3.0Sulphur, max 0.25

Insoluble residue-.. 10.30

The briquettes melt during the 20-25 minute roasting period and we havefound that the metallic molybdenum reduced from the molybdenum after themelt.

i We make use of'no special slag but prefer a slag having approximatelythe following composition:

Per cent Silica 16-20 Alumina 4-6 Manganese dioxide 3 Phosphoruspentoxide 1 Ferric oxidea 70-4-76 The molybdic oxide briquettes cause nocarbon pick-up since the entire carbon content thereof is utilized inreducing the molybdenum tri-oxide through several stages to metallicmolybdenum;

all of the carbon being converted into carbon dioxide (CO2) which passesoil as gas.

The following data was derived from tests carried out on six bars of ouralloy wrought iron, the analyses of which read as follows:

Per cent and maintain them at the desired temperature during the quicktensile test.

The temperature of the furnace was automatically controlled to within or5 F. of the specified temperature. Two thermocouples were used todetermine the temperature of the test specimen. One of thesethermocouples was at one end of the gage length and one at the other.The temperature differential between these two thermocouples neverexceeded 5 F. throughout any of the tests. i

The tension specimens were brought up to the desired temperature andheld at that temperature thirty minutes before any load was applied.During thetest the cross-head speed of the machine was controlled at'.05 to .06" per minute.

Yield points were determined from the plots as recorded by the automaticauto'graphic indicator of the Tinius-Olsen testing machine.

We have found that the addition of from .20 to.- .50% molybdenumincreases the tensile strength of wrought iron at room temperatures byfrom 1500 to 2000 pounds per square inch, and

that when subjected to the higher temperatures ofmodern locomotive fireboxes, stay-bolts made from our alloy wrought iron have a tensilestrength of from 5000 to 6000 pounds per square inch greater thanstay-bolts made from typical double refined wrought iron.

We have also found that the addition 'of molybdenum withinthe range usedby us results in a finer and more homogeneous grain structure. This isof distinct advantage, since a large. perard 2" gauge length testspecimens were machined from diiferent bars. Duplicate tension testswere run on bars of each identification number at room temperature, at400 F., at 750 F'. and at 900 F.

The bars were set up in special holders in a hydraulic tension testingmachine. A resistance centage of the stay-bolts are furnished with C.013.04 either a 1%" 0r diameter hole drilled par- Mn .05 -.06 tially orthroughout their entire length. These P .102-.127 are then threadedeither partially or throughout S .009.014 their entire length. i Si-.099.141 We have found that articles such as stay-bolts Cu' .040-050and engine bolts made from hot rolled material M0 -.39- -.48 embodyingour invention are much freer from Room temperature 1331.10 100 100 101101 100 -100 100 100 107 107 101 101 Yield 01110 0. 34,700 37,100 30,00030,000 30,300 33,000 37,400 34,700 37,000 33,500 37,400 35,200 Tensilestrength, 52,200 52,100 52,200 52,200 52,000 52,800 52,300 52,300 52,50052,300 52,700 52,500 Elong., 101011110--.. 30 32.5 31 31 31 34 33 31 3431 31 31 R. 5, 01,200...." 40.0 50.0 49.0 51.0 50.0 52.5 51.5 40.5 50.048.5 50.0 51.5

00 F. Yield 01110. 5. i. 30,800 31,400 .500 31,000 33,000 32,200 34,10031,100 34,000 30,500 32,500 Tensile strength, p. 03,700 73,000 72,40074,000 71,500 71,500 72,100 70,700 70,000 00,000 73,700 131011 3.,percent" 21 20 20 21 20 20 20.0 21 21 21 21 R,A,,percent 34.5 35.0 34.536.5 37.0 -36.0 38.0 30.5 38.0 39.0 37.0 33.8

Yield 501111, p. 0.1 27.300 21,440 27,300 25,200 27,500 30,300 28,28,850 Tensile strength,p 57,600 57,600 57, 00 55, 500 58,000 60,50059,100 59,100 E1ong., 0100111..-. 20 25 20 20 20 25 24 25 R. 14.,percent 49.0 48.5 48.5 40.5 49.5 40.0 47.5 48.0

wow.

31510 0111 01 25.100 24.300. 24.000 24.000 20.050 23,450 23,500 22,40025,300 24,500 22,000 Tensile strength, p. s.i L- 43,0 43,500 43,50043,200 00 44,300 42,800 42,600 41,500 43,200 43,600 42,600 Elong.,percent 24 24 24 25 2 24 23 23 25 24 24 24 R.A.,percent 53.0 -0 -5 -455.0 54.4 54.0 54.0 53.5 53.7 02.0 52.5

In making the above tests, A. S. T. M. standscale and have fewer surfacepits and other sur- The method of making alloy tionally incorporated asubstantially uniformly distributed quantity of slag in an'amount suchas is normally present in wrought iron; said alloy containing from about.10% to about 1.00% molybdenum, carbon less than about .06%, with thebalance substantially all iron except for said slag and the usualimpurities present in wrought iron.

2. An alloy wrought iron aggregated from a solidifying mass of pastyparticles of highly refined metallic iron alloyed with molybdenum,

with which, without subsequent fusion is intentionally incorporated asubstantially uniformly distributed quantity of slag in an amount suchas is normally present in wrought iron; said alloy containing from about.20% to about .50% molybdenum, carbon less than about 05%, manganese notover .06%, with the balance substantially all iron except for said slagand the usual impurities present in wrought iron.

3. An article which, during use, is subjected to relatively hightemperatures and vibratory stresses; said article being fabricated froman alloy wrought iron aggregated from a solidifying mass of pastyparticles of highly refined metallic iron alloyed with molybdenum, withwhich, without subsequent fusion, is intentionally incorporated asubstantially uniformly distributed quantity of slag in an amount suchas is normally present in wrought iron; said alloy containing from about10% to about 1.00% molybdenum, carbon less than about .06%, with thebalance substantially all iron except for said slag and the usualimpurities present in wrought iron.

4. A bolt fabricated from an alloy wrought iron aggregated from asolidifying mass of pasty particles of highly refined metallic ironalloyed with molybdenum, with which, without subsequent fusion, isintentionally incorporated a substantially uniformly distributedquantity of slag in an amount such as is normally present in wroughtiron; said alloy containing from about .20% to about .50% molybdenum,carbon less than about .05%, manganese not over 06%, with the balancesubstantially all iron except for said slag and the usual impuritiespresent in wrought iron.

JOHN W. DAVIS. RAY McBRIAN.

